It is known to provide sports shoes or walking boots, and in particular soccer shoes, with studs in order to increase the grip of the shoe, in particular, on soft ground such as grass. The term "studs" is to be understood in the context of the present invention as meaning all possible elements which are arranged on outsoles of footwear in order to increase grip. The term "studs" is intended to include; for example, conventional studs for soccer shoes, spikes as are used for sprinting shoes, and studs for walking boots. Only conventional soccer shoes are described in the following description of the prior art and the invention, however, it is the intention to also encompass all possible types of studs within the above meaning.
The use of studs on soccer shoes has long been known. The studs used originally formed an integral part of a soccer shoe outsole, which is usually made from plastic. This, however, had the drawback that the studs quickly wore down, in particular, as a result of running on hard surfaces, such as asphalt, resulting in the need to replace the entire shoe when the wear reached a critical level.
Furthermore, it was not possible to use studs adaptable to changing ground conditions or to adapt the shape and length of the studs to meet the individual needs of a player. If the ground conditions changed, and therefore the studs were unsuitable, it was necessary to use a new pair of shoes with the appropriate studs. Shoes with studs designed for particular requirements were expensive custom-made articles.
For this reason, studded footwear provided with exchangeable studs has long been offered. It was easy to provide exchangeable studs in the case of studs of round cross-section or with rotational symmetry, which were conventionally used. The stud, now usually made of metal, was simply screwed on to the outsole by means of a screw thread. With this known technique, it was possible by using self tightening screws to ensure that the screw connection between sole and stud did not become detached.
For some time, however, the prior art has been moving away from the use of round or rotationally symmetrical studs, since in many instances these studs no longer are able to satisfy current requirements with regard to optimum grip when quickly changing direction or sprinting or both. Therefore, it is now preferred to use elongate studs that have been optimized for particular types of sports with respect to their shape and orientation on the outsole.
The use of elongate or asymmetric studs, however, can cause problems because their orientation in the fitted state, as explained above, is important to the performance of the article of footwear. For this reason, the conventional connection between outsole and stud by means of a screw mechanism is no longer suitable, since attaching and tightening the stud does not result in a final defined position of the stud. Therefore, it has been necessary to find alternative fastening mechanisms for elongate or asymmetric studs to allow such studs to be fitted in the desired orientation or position with respect to the sole of the footwear. To avoid the risk of injury and to provide the desired grip properties, it has been necessary for suitable fastening mechanisms to fasten studs so that they are secured against rotation.
A possible fastening mechanism for elongate or asymmetric studs of this nature is described in U.S. Pat. No. 5,628,129. According to this known approach, an outsole is provided that has a plurality of receiving openings for studs that include a base part and a grip part. The base part comprises a plurality of engagement projections that extend from the base part on the circumferential side. In order to connect the stud to the outsole, the engagement projections are introduced into the receiving openings in such a manner that the engagement projections are in alignment with engagement notches that are provided in the receiving openings of the outsole. The stud is then fixed to the outsole by rotating the stud through a defined angle.
A further possible solution to the problems discussed above is disclosed in European patent no. 0,815,759. The elongate, exchangeable soccer studs described in this document have a polygonal base which can be introduced into a recess of complementary design in an outsole. In this way, it is ensured that the elongate stud can be fastened in a rotationally secure manner in the desired orientation. As with the conventional approach, the connection between stud and outsole is achieved by means of a screw that extends through a continuous opening in the stud into a screw thread of corresponding design in the outsole. In this case, the screw head is situated inside a recess in the outer end of the stud.
The solutions that are known from the prior art have a large number of drawbacks. For example, a substantial rotary force exerted on the stud built in accordance with U.S. Pat. No. 5,628,129 may cause the stud to become unscrewed from the receiving opening, resulting in a considerable risk of injury.
For an exchangeable stud in accordance with European patent no. 0,815,759, problems arise as a result of the fact that the screw head is arranged inside a recess in the outer end of the stud. In particular, if the screw becomes loose unintentionally, the large number of sharp edges may create a considerable risk of injury, particularly if players come into contact with the studs. For this reason alone, such a design likely would not be licensed by the Federation International Football Association (FIFA).
Furthermore, practical problems arise; it is clear that when the shoe is used, for example, on grass, the stud becomes very dirty with the result that it requires considerable effort to exchange the stud. In addition, when running on hard surfaces the wear to the outer end of the stud quickly leads to the screw head or other fastening mechanism that is generally normal to the sole of the shoe and disposed on a wear surface of the stud becoming abraded, making it impossible, or at least difficult, to exchange the stud and rendering the fastening mechanism non-reusable. Furthermore, the outer surface of the stud is usually relatively small in order to allow it to penetrate optimally into the ground. Due to the size requirements of the stud, it is only possible to use a comparatively small screw, since the screw head should never project beyond the end face of the stud. If it is only possible to use small screws, then the stud fastening may be insufficient. Also, exchangeable studs that require multiple parts for attaching to a shoe may be difficult and time consuming to exchange. For example, loose parts, in particular, relatively small parts can be hard to handle and susceptible to becoming lost.
An objective of the present invention is, therefore, that of providing exchangeable, preferably elongate studs for footwear which meet FIFA requirements with regard to the risk of injury and the reliability of the connection and which can be produced inexpensively and exchanged without problems.